Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 15.1	$ 12.2	$ 42.7	$ 25.9
Reclassification of de-designated interest rate collars		0.4	0.5	1.2
Foreign currency translation loss	(0.6)	(0.1)	(0.7)
Comprehensive income	14.5	12.5	42.5	27.1
Less: Comprehensive income attributable to noncontrolling interest	0.8	0.7	2.3	3.1
Comprehensive income attributable to SP Plus Corporation	$ 13.7	$ 11.8	$ 40.2	$ 24.0